Gensler’s Thames river park sent back to drawing board

Gensler’s proposed 1km-long floating park on the River Thames is to be redesigned and will not now be completed in time for the London 2012 Games

A spokesman for project backers the London River Park (LRP) remained ‘committed to the scheme’ but would not confirm if the practice would be retained to carry out the revisions. The review has been brought about in response to criticism from DC CABE, ‘residents and river users’ (see full letter from the LRP to the City of London planners).

In November the Port of London Authority (PLA) said it could not give the project its support, even though it already had the Mayor’s rubberstamp, until ‘serious concerns’ about the scheme’s impact on navigational safety had been resolved.

As a result the City of London put back a decision on the walkway proposals originally scheduled for 15 November (see below).

A spokesman for LRP said: ‘In light of feedback from river users in particular we are going to be revising. What those revisions will be is exactly what the team is presently looking at.

‘As we have said, the scheme is presently under review. Gensler have done an excellent job developing the concept of the river park to date, but at this stage we have not yet considered whether or not there will be changes to the architects involved.’

LRP said ‘new proposals’ would be brought forward ‘in the early part of 2012’.

Previous story (AJ 04.11.11)

Serious safety concerns stall decision on Gensler’s floating walkway

The City of London has put back a decision on Gensler’s proposed 1km-long floating park on the River Thames after ‘serious concerns’ were raised about the scheme’s impact on navigational safety

The authority’s planning and transportation committee was expected to consider the plans for the £60 million London River Park at its next meeting on 15 November 2011.

However the City received a letter from the Port of London Authority (PLA) yesterday (3 November) saying it could not give the project its backing until it had discussions with the design team ‘to see if it [was] possible to resolve the outstanding issues’.

As a result the City has deferred its own decision until a later date.

Fears that the proposed project could could speed up and divert the river flow - and in turn risk scouring bridge abutments along the route - were reported by AJ’s sister title New Civil Engineer last month (see below).

Chairman of the City of London Corporation’s planning and transportation committee, Martin Farr, said: ‘It is unfortunate that, at this time, the committee is unable to consider this proposal.

‘In order to properly exercise its duty as the local planning authority, the City’s planning and transportation Committee needs to be able to consider all of the material facts.

‘We look forward to receiving further information as to whether the issues identified can be resolved.’

Gensler had hoped to complete the project, which includes two 10 metre wide floating pontoon sections, in time for the Queen’s Jubilee Celebrations and the London Olympic Games next year (2012). London Mayor Boris Johnson has already given the plans his rubberstamp.

Earlier this week project backer, the Southeast Asian-based Venus Group, warned it could take scheme to Singapore if London refused to grant it permission (AJ 03.11.11).

A spokesman for Gensler said: ‘Gensler fully understands the City’s position and it hopes for a speedy resolution of any outstanding issues’

Previous story (AJ 21.10.11)

Gensler’s floating walkway a threat to London bridges

Gensler’s proposed 1 km floating park platform on the River Thames could alter its flow and damage the capital’s bridges, sources close to the scheme claim

Speed and divert river flow

Concerns have been raised that the proposed £60 million London River Park project could speed up and divert the river flow, which in turn poses the risk of scour to bridge abutments along the route, reported sister title New Civil Engineer.

Promoter London River Parks − comprising architect Gensler, project manager Mace and private investor Venus − submitted its detailed planning application on 18 July for the 1.6 kilometre-long walkway along the north bank of the river. The walkway is supported by floating pontoons.

The walkway’s route from the Millennium Bridge east to Custom House is in a section described by river regulator Port of London Authority (PLA) as the ‘busiest part of the river, characterised by a number of bridges in close proximity and strong tidal flows’.

Key infrastructure along the route includes London Bridge, Cannon Street Railway Bridge and the Millennium Bridge.

Plans include two 10 metre wide floating pontoon sections − a 420 metre long western section between Blackfriars Bridge and Southwark Bridge and a 540 metre eastern section between Cannon Street Railway Bridge and Custom House. These are divided by a central inland river bank section about 600 metre long.

The floating sections are to be secured by a series of 800 millimetre to 2.6 metre wide precast concrete piles up to 16 metre deep.

Displacement ‘could lead to scour’

It is these two pontoon sections that pose the greatest risk to the river infrastructure, said the source. The water displacement caused by the pontoons could divert the river flow so that it causes scour on the abutments.

It should be properly mitigated before the scheme gets the full go-ahead, said a source close to the project: ‘Scour can build up quickly.’

The threat of scour could also be exacerbated as the reduced width of the river will increase the speed of the current, he added.

HR Wallingford principal scientist John Baugh said that neither the river flow nor speed will greatly alter as a result of the pontoons.

‘Our tests show that the river speed changes by just 0.2 knots in extreme conditions, against an existing flow of between 2.5 and 4 knots,’ he said.

Baugh added that the testing, which includes a 1 in 100 scale mock-up, backs-up the theory.

However, sources close to the scheme believe the effects of the river flow should be assessed in a permanent rather than temporary condition.

Fears for permanent fixture

While London River Parks has applied for a five year temporary planning permission, the source said there are concerns that if successful it could become a permanent fixture on the river in a similar way as the London Eye on the city’s South Bank. It was also built with temporary planning permission.

Mace project manager Jon Pettifer said that the scheme will be up for only five years but acknowledged that there have been concerns with the reduced river navigation.

He said that there would not be a great impact. He added that the project team should work closely with PLA to ensure that river traffic is not disturbed. However, river traffic could create a further problem for bridges, said the source.

By reducing the navigable width of an already very narrow part of the river there could be a greater likelihood of vessels striking the bridges.

‘We’re working with PLA to ensure that there is no adverse impact,’ said Pettifer. He said that PLA conditions state that the pontoons must be between 8m to 10m away from the main navigation channel, and the current configuration meets the requirements except in two small areas.

The City of London Corporation will decide whether to approve the scheme on 14 November.

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